Sealed AGM Batteries

Off Grid Solutions:-

Battery sizing guide,

For an off-grid house, the battery is sized to deliver about 3 to 5 days of power while being discharged up to 60% of capacity. Less than 3 days capacity means you’ll be cycling the battery heavily on a day by day basis and this isn’t great for life expectancy.

Why only take 60% of the battery capacity? The more deeply you cycle a battery, the fewer charge/discharge cycles you’ll get out of it. You can cycle your battery to 100% of capacity if you want but after a handful of cycles, you’ll be buying a new one. True deep-cycle batteries are rated for how many 80% depth of discharge cycles they’ll tolerate.

To raise the voltage you connect cells in series. To raise the amp-hours you use bigger cells or you connect them in parallel. Large household sized battery packs can consist of many small batteries connected in series and parallel to deliver the voltage and amp-hour capacity needed. It can also consist of a few large cells in series. As a general rule, battery packs with a few large cells are going to last longer, be easier to move around and less time-consuming to maintain, have fewer problems, but the initial cost higher.

In order for the battery bank to run flawless batteries must all be the same age, same size, and same brand. Any deviation to those conditions will cause smaller batteries to work extra hard, and larger batteries to loaf and sulphate.

Battery Council International (B.C.I.) is a trade organization that sets standards for the batteries, including sizing codes. Some batteries have acquired less-official names from their intended use— for example, “GC2s” got theirs from being used as golf cart batteries. Batteries with the same code or name will have approximately the same dimensions, but their capacities may differ significantly, especially between flooded or sealed units.

This table gives you the standard values accepted by B.C.I. for different groups type of batteries existent on the market.

Battery Type

Nominal Voltage

Capacity AH (C20 rate)

Weight (lbs)

Dimensions (Inches)

U1

12

33

24

8.5 x 5 x 7

Group 24

12

75

54

11 x 7 x 10

Group 27

12

92

63

13 x 7 x 10

Group 31

12

105

70

13 x 7 x 10

Group 4D

12

200

130

20 x 8 x 10

Group 8D

12

250

160

21 x 11 x 11

Golf Cart battery

6

225

62

10 x 7 x 11

L16

6

400

120

12 x 7 x 17

Deciphering Capacity Specifications,

Deep-cycle battery capacity is rated in amp-hours (Ah). The power equation dictates the relationship between amps, volts, and watts: A × V = W. When you add in the time factor for figuring energy capacity, the same holds true for the relationship between Ah and Wh: Ah × V = Wh.

To compare the energy capacity of batteries of different voltages, the easiest way is to convert to Wh. For example, a 250 Ah,6 V battery has half the capacity of a 250Ah, 12V battery.

6 V × 250 Ah = 1,500 Wh
12 V × 250 Ah = 3,000 Wh

Battery capacity specifications also depend on how quickly the battery is charging or discharging. The faster the charge/ discharge rate, the less overall capacity a battery will have. For example, a battery may have a 100Ah capacity when powering 2A of LED lighting, but only 75Ah with 8A of compact fluorescents. To make matters worse, not all battery manufacturers clearly show what the charge/discharge rates are for the Ah ratings on their spec sheets. It’s common to see C/100 rates (quite slow) to make a battery look like it has more capacity.

Most folks in the RE world like to use a C/20 rate, which is close to the typical daily (24-hour) cycling found in RE systems;

The information posted herein has been compiled by Clean Energy Brands from OEM product data and reputable publications. All rights reserved!